Influence of Temperature on Fatigue Crack Propagation in TiAl Alloys

Experimental investigations of fracture toughness for a TiAl-based γ-alloy were performed at different temperatures. The temperature effect on fatigue crack growth behavior is evaluated, the formula describing its rate in range to II (stable propagation) was derived, as well as specific values of equation constants were obtained on the basis of experimental results. Tests were conducted in vacuum at 25, 750, and 850°C. The experimental results demonstrate that temperature exerts great influence on fatigue crack growth rates. With an increase in temperature up to 750°C, the growth rate of such cracks increases, after reaching this temperature, the brittle-ductile transition of a TiAl-based alloy is taking place. A similar relationship is also observed for conventional alloys.